Process of obtaining illuminating-gas from lignite



" is expenslve UNlTED STATES PATENT OFFICE.

, EUGENE P. SCHOCH, OF AUSTIN, TEXAS.

PROCESS OF OBTAINING ILLUMINATING-GAS FROM LIGNITE.

No Drawing.

T a2? whom it may concern:

Be it known that I, EUGENE P. SoHooH, a citizen of the United States, residing at kustin, in thecounty of Travis and State of Texas, have invented certain new and useful Improvements in Processes of tainlng lllumlnating-Gas from Lignite;

and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process of obtaining an illuminating gas directly from lignite, without having to enrich the same, and has for its object to improve the procedures heretofore proposed.

With this and other objects in view the invention consists in the novel steps and combinations of steps constituting the process, all as will be more fully hereinafter disclosed and particularly pointed out in claims.

In order that the exact invention may be the more clearly understood it is said: The gas ordinarily obtained through the dry dis.- tillation of lignite, such for example as that found in Texas, has a calorific power of say from 400 to 450 British thermal units (hereinafter referred to as B.- T. U.) per cubic foot, althou h some investigators put it as high as 450 T. U. This gas upon investigation may be shown to contain sa from 18% to 22% of carbon dioxid, C 2 and therefore by removing thelatter, the calorific power of said gas can be raised to say 500 to 550 B. T. U. But as is well known these figures are too small for a satisfactory illuminating gas, which latter requires a calorific power of at least 600 B. T. U.

Therefore it has been heretofore proposed to suitably enrich the gases obtained from lignite when they are to be employed for illuminating purposes, but such procedure and is attended by other objections not necessary to mention. a

It has further beenproposed to secure a rich high temperatures in a retort, and by taking off separately the various gases corresponding to the said temperatures, in the belief that some of the fractions thus obtained wouldibe sufiiciently rich in calories tobeused as a city illuminating gas.

But I have found from practical tests Specification of Letters Patent.

' (about 400 cubic feet gas by heating the lignite to various that as the lignite rises in temperature the only portion ofthe gas given off that is rich enough for a city gas, is evolved at a relatively low temperature and is relatively small in amount, or as low in volume one fifteenth of the total. I have further found that those portions of the gas evolved from the lignite after this said rich portion, have heating powers of only about 430 B. T. U. that they amount in volume to about 4500 cubic feet per ton of lignite, while those portions evolved before this said rich portion, have heating powers lower than 430 B. T. U. and amount to about 1000 cubic feet per ton.

It will thus be seen that out of say, 5900 cubic feet of gas per ton of lignite obtained by this method only a negligible fraction is really rich enough to be used directly as a city gas and no amount of fractionation can change the results.

Upon a further investigation of these fractions, I have found that the percentage known as Bastrop lignite and when the in-.

side of the retort just above the li nite was at a temperature of 325 C. and t e inside bottom of the retort was at a temperature of 590 (3., I found the percentage of carbon dioxid CO present, to decrease suddenly from say 40% to say 20% or less, also that the amounts of methane, ethane and illuminants also decreased markedly, and that these decreases occurred at about the same temperature at which the hydrogen and carbon monoxid increased. I found substantially the same phenomena when using what is known as Milam Co. lignite when the inside of the retort just above the lignite was at a temperature of 310 C. and the inside bottom of the retort was at a temperature of 575 0.

fractions it became apparent that these changes in composition are so related, or are so balanced each against the other as to leavethe heating power of the total volume of gas aboutthe same or at say 430 B. T. U.

v Patented Jan. 4, 1921. 7 Application filed August 30, 1919. Serial No. 320,930.

as say if we consider the Bastro p lignite. It further became apparent that the low heating powers of the gas portions evolved at high temperatures or after the CO has markedly decreased are not due to the presence of carbon dioxid while the lowheating powers of said gas portions evolved atlow-temperafractions can be separated from the earlier,

and the "earlier separated from their CO content, then the earlier will have a high heating power. 7

In pursuing my tests I still further discovered that I could collect samples of gas at the lower temperatures which contained as much as 30% CO and which with this ()0 present had'a heating power as high as 450 B. U. v

In fact from average tests made on Milam Co. lignite I obtained an earlier 'gas fraction havin 32% CO and a. heating power of 455.5 T. U. when burned with its CO present. mediately followed that if I removed this content of CO, from these earlier or lower temperature fractions I would obtain a large volume of gas havin the desired high heating power above 600 T. U.

Accordingly in carrying out my invention I obtain a city illuminating gas having a heating power above 600 B. T. U. and in relativcly large proportions directly from lignite by subjecting the latter to a destructive distillation in a retort, and separating out the lower temperature fractions or those fractions which are relatively rich-1n carbon dioxid from the higher temperature fractions, or those fractions which are relatlvely poor in carbon dioxid. The exact percentage of carbon dioxid which determines the dividing line between the lowera higher heating power than 600 B. T. U. is

desiredor a heating powerupto say 670 B. T. U. then thatportion of the evolved gas that will be selected for a cit gas will show such a high percentage of C3 as will, when removed, permit the gas to yield the desired heating power. lar e'arlier fractions mentioned above .as containing 32% CO showed by both calculations and test that when the CO was removed it had a heating power of 670 B. T. A later fraction might have showed such a low percentage of CO that when burned without said CO its heating power would that they will Having reached this result, it im- For example the particu be below 600 B. T. U. yet if this said later fraction were separated with said earlier fraction the two could easily show a heating power after the removal of the CO well above 600 B. T. U. i

It will now be clear that my process in volves the recovery and separation of lower fractions of gas that are so rich in CO that when burned with their CO content they will yield calorific powers well below 600' B. T. U but on the other hand when burned without their CO content they are so rich in constituents of high heat giving powers yield a calorific power .above 600 B. T. U.

The separation of the carbon dioxid from the recovered city gas making fractions may potassium carbonate solution; I havefound no diflicultyin thus reducing the amount of CO present down to say and thus raising the heating power of the'city-fraction gas from say 450 B. T..U. to 6&7 B. -'T. U.

After the potassium carbonate solution has thus become saturated with carbon dioxid, it

* may be regenerated in the usual manner by heating it until the absorbed carbon is expelled; and then it may be used over again.

The heat used for this regenerating purpose is the main operating cost encountered but it may be obtained from the waste gases of the process that are too poor for other pur poses.

I have. further discovered that in carry ing out this process for making a city gas from lignite, practically the whole of the I tar that is formed in the retorting operation is obtained during the formation of this city gas making fraction, sosaid tar is recovered as a by product, and goes to partially defray the expense of the operation.

That is to .say, the economic retorting of lignite requires the preparation and disposition of all products, and among these are the coke residue, and the tar. The cokev residue should be as rich in combustible components as possible, provided it is ofsuch a nature that briquets madefrom it will not explode or disintegrate in a fire. Such a coke residue is obtained if the retorting is discontinued after removing the fraction I convert into a city gas. And,

at the same time, .I secure all of the tar,

from which I may make various valuable products such as oils, parafiin, or asphaltic residues for briquet binders, etc.

Q It is obvious that those skilled in the art gas from lignite which consists in subjecting said lignite to a fractional distillation until the percentage of carbon dioxid evolved shows a marked decrease, thereby evolving at lower temperatures producing fractions of gases of relatively high illuminating powers mixed with substantial percentages of carbon dioxid; recovering said fractions; and removing the carbon dioxid present from said fractions. substantially as described. I

2. The process of making an illuminating gas from lignite which consists in subjecting said lignite to a distillation process until the percentage of carbon dioxid evolved with the other gases shows a marked decrease; collecting all the gases thus produced; and separating out the carbon dioxid present, substantially as described.

The process of making an illuminating gas havin a calorific power exceeding six hundred firitish thermal units, which consists in subjecting lignite to a distillation process of increasing temperatures and until the percentage of carbon dioxid evolved with the othergases begins to rapidly decrease; collecting the gases thus produced; and separating out the carbon dioxid present, substantially as described.

4. The process of making an illuminating gas having a calorific power exceeding six hundred ritish thermal units, which consists in subjecting lignite to a fractional distillation process of increasing temperatures and until the percentage of carbon dioxid evolved with the other gases decreases by as much as five per cent; collecting the gases thus produced; and separating out the carbon dioxid present, substantially as described.

The process of making an illuminating gas having a calorific power exceeding six hundred British thermal units, which consists in subjecting l-ignite to a distillation process of increasing temperatures and until the temperature of the lignite exceeds 290 and the percentage of carbon dioxid evolved with the other gases has substantially decreased; collecting the gases thus produced; and separating out the carbon dioxid present, substantially as described.

6. The process of making an illuminating gas suitable for city use directly from lignite which consists in subjecting said lignite to fractional distillation until the percentage of carbon dioxid evolved shows a marked decrease; separating out those fractions of the evolved gases which are rich in carbon dioxid; and removing said carbon dioxid from the gases thus recovered, substantially as described.

In testimony whereof I affix my signature, in presence of two witnesses.

EUGENE P. SGHOCH. Witnesses R. A. MoNnEs, ROBERT S. TAYLOR. 

